Earth travels around the Sun, and one trip takes about a year, or about 365 days. Earth is tilted by about 23 and a half degrees. As Earth goes around, its tilt always points the same way in space. Earth does not wobble back and forth each year.

Many people think summer comes when Earth is near the Sun. That is not true. Earth is closest to the Sun in early January, in the middle of northern winter. It is farthest from the Sun in July. This is true as of November 2026. The distance to the Sun is not what makes summer hot or winter cold.

The tilt works through the Sun's rays. In summer the Sun is higher in the sky, and its rays hit the ground more directly. That makes summer warmer. In winter the rays hit the ground at a slant, so they spread out over more ground and warm it less.

The tilt also changes how long the Sun is up. Summer days have more hours of sunlight, and winter days have fewer. The summer solstice is the longest day of the year in the north part of Earth. The winter solstice is the shortest day and longest night.

The summer solstice in the north is usually June 21, and on that day the Sun is directly over the Tropic of Cancer. Around December 21 the Sun is directly over the Tropic of Capricorn. That is the winter solstice in the north and the summer solstice in the south.

Twice a year, day and night are about equal in length. Each of those days is an equinox. The word comes from Latin words that mean equal night. The spring equinox is usually on March 20, and the fall equinox is usually on September 22.

Trees feel the calendar too. In late summer the days get shorter, and that tells trees to make less green chlorophyll. Less chlorophyll lets other colors show, so leaves turn yellow, orange and red.

The two halves of Earth have opposite seasons. When the north part leans toward the Sun, the south part leans away from it. So when it is summer in the north, it is winter in the south.

Words to know

• solstice: extreme day
• equinox: equal night
• chlorophyll: leaf's green

The short version

Earth has seasons because it is tilted by about 23 and a half degrees as it goes around the Sun. The tilt changes how directly the Sun's rays hit the ground and how many hours of sunlight each day has. Earth's distance from the Sun is not what makes summer or winter.

Quick facts

• Earth goes around the Sun once about every 365 days.
• Earth is tilted by about 23 and a half degrees.
• The summer solstice in the north is usually June 21; the winter solstice is around December 21.
• At an equinox, day and night are about equal in length.
• Earth is not closer to the Sun in northern summer.